Although speakers appear rather unassuming
in their design (a box with one or more drivers attached), there
is a great deal more to them than what most people realize.
Granted, most speakers are the ubiquitous front-radiating dynamic
transducer variety, but there are also many ribbon and
electrostatic speakers, as well as what Mirage is best known for:
the bipolar radiator.

What's the difference?

I'll start with a brief description on the
various types of speakers. First, the dynamic front radiator.
These are the most common type (should I use the term
"garden variety"? OK, I'll use it, but the more
scientific term is "MONOPOLAR"), completely surrounded
with an enclosure usually made of MDF. The drivers are cones,
attached to a metal frame, and which move piston-like when
activated by the amplified electrical signal (the music). They
actually radiate sound forward and backward (below certain
frequencies, when the wavelength of the reproduced sound becomes
larger than the diameter of the effective radiating cone, this
becomes a 360-degree radiator). The back-wave is at least
partially absorbed within the enclosure by damping material, such
as wool or fiberglass, along with the material of the enclosure
itself (usually MDF). Otherwise, the back-wave from some of the
frequencies (particularly the low end) would cancel the front.
Ports (vents) are found on many enclosures, and contrary to what
some users think, the air coming out of a port does not interact
with the air moved by the active driver to produce cancellation,
but rather, enhances the total production of the sound wave (at
least in a properly "tuned" port) of the loudspeaker's
low frequencies.

The second type is what is known as a
DIPOLE radiator. This can consist of two cone speakers, one
mounted on the front of the enclosure, and the other on the back.
The two speakers are wired so that when the front driver is
moving out of the enclosure, the back driver is moving into the
enclosure. Dipoles can also be made from long, thin pieces of
metallic (coated) material that are suspended at both ends (or in
the case of some, like the Quad's, many individually suspended
pieces) and driven by the signal. [Click HERE here to go to description of speaker types in the
primer] Sound radiates, again, both backwards and forwards. This
time, though, the back-wave is allowed to travel back through a
grill (cloth in the case of planar-magnetic speakers, metal in
the case of electrostatic speakers) that is acoustically
transparent, into the listening room, and this back-wave is
180-degrees out of phase with respect to the front-wave. As a
result of this, placement of dipoles is critical if one is to
avoid a loss (cancellation between the front and back-waves) of
frequencies below 100Hz or so. In fact, if you stand at the side
of these speakers, you will be in an area where the front and
back-waves are canceling each other at low frequencies, and,
thus, dipoles are also called figure 8 radiators.

Mirage first marketed the BIPOLAR design in
loudspeakers, and their line includes the M-590i, M-890i,
M-1090i, M7-si, M5-si, M3si, and M1-si. Bipolar subwoofers
include the BPS-100, BPS-150, BPS-250, and BPSS-210. Mirage also
makes other models that are not bipolar (they are of the forward
radiating variety). The bipolar radiator has both front and rear
waves fired in phase, that is, when the front radiator is moving
away from the enclosure, the back radiator is also moving away.
This means there is virtually no sound wave cancellation at the
sides, compared with dipoles. In practice, the effect one gets
(and borne out by listening) is a wider sound-stage with maybe a
little less precise imaging than with the best monopolar
mini-monitors (I am glad I only had to type this tongue twister
instead of having to say it). Dipolar speakers, by the way, also
have the less precise imaging, but expanded sound-stage, compared
with monopolars. Some users feel that this phenomenon is actually
more "natural" than the sound produced by front
radiating designs. Was this what I got with the M1090i bipolar
speakers? On with the review...

Setup
Physically, the 1090is are 45 3/8"(H) x 11 1/2"(W) x 9
1/2" D. This is pretty big, but the cabinet, which consists
of a polished black top plate on top and an acoustically
transparent sock all around (like all the other bipolar Mirages)
make it look very elegant. Fiberglass damping is used to reduce
standing waves and to help dissipate heat as well as to promote
higher power handling with lower distortion. Another damping
material, constructed from wool and man-made fibers, is used to
reduce cabinet resonances that are not completely controlled by
the MDF structure and internal bracing. The driver complement
consists of two 6 1/2" injection molded polypropylene cone
woofers and two 1" titanium vapor deposited on cloth dome
tweeters (the ones used in the 1090i's larger siblings, the M-1si
and M-3si, are solid titanium domes rather than cloth). The
tweeters are mounted about 5 1/2" from the top plate,
slightly off-center, and the woofers below. One set is on the
front, and the second set is mounted behind. A 2 1/2"
(diameter) port can be found at the rear, about 9" from the
bottom plate. Electrical connection is made with two sets (for
bi-wiring or bi-amping) of 5-way binding posts just below the
port. These have a plastic nut, so hand-tighten you must!

I put the 1090is where my pair of Magnepan
SMGcs normally sit, about 6' apart, and 33" from the back
wall. The distances to the side walls are unequal, as to the
right I have a wall about 24" from the right loudspeaker,
but the left sees an open space which leads to the dining area. I
listen about 8' away and to compensate for a slightly shifted
center image, I sit on the right end of the sofa (which is the
same distance from both speakers) and most of the other end lies
on the left (i.e., the left speaker "sees" more sofa
than the right).

The Mirages come with spikes that are not
easy to screw in. I actually set them up and listened to Joe Beck
("The Journey", DMP CD481), moving them this way and
that, getting the deeper bass stronger and trying to remove some
of the emphasized mid-bass (about 100 - 200Hz, as measured with
my trusty Radio Shack SPL Meter and Stereophile's Test CD 1)
before I put in the spikes. Things got better though on certain
CDs ("The Fairfield Fours' Standing in the Safety
Zone", Warner Brothers 9 26945-2), male voices were rather
chesty. As I listened, I decided it was something I could put up,
and I wasn't entirely sure at this point that the Maggies were
exactly the opposite in the 100 - 200Hz range. On them (the
Maggies), male voices sounded, by comparison, a little
light-weight, with some of the (musically pleasant) lower tones
recessed in the SMGc's presentation. Of course, the chestiness
could be a result of the room acoustics, and aberrant colorations
can be a thorny issue with bipolar and dipolar designs, which are
very sensitive to the room in which they are placed. Listening to
the Test CD through the 1090is, I was able to hear an intense
30Hz, but almost nothing at 25Hz.

The upper octaves were terrific, extending
(it seemed to me) even higher than the Magnepans go, and sounding
sweet with "normal" playing volume, but with just a
trace of hardness when I drove them loud. On Reference Recordings
"From the Age of Swing" with Dick Hyman (RR-59CD), the
sense of air around the musicians was immense. When I first
played this CD, the front half of my room disappeared (I wonder
if the 7.7 earthquake last night had something to do with that).
I thought the Mirages might be exaggerating this effect until I
put on Kenny Loggins' "Nightwatch" (Columbia CK 35387),
when the sound stage closed in appropriately. Imaging did not
suffer, however, as I though it might, due to the bipolar design.
Images (the musicians) were easily located in space between and,
depending on the recording, even beyond the 6' setting of the
1090is.

My last test was with laserdiscs, to see
how the Mirages would perform in a home theater system. Playing
"Jurassic Park", "The Abyss", and "True
Lies", the 1090is proved they could reproduce intense sound
tracks without any difficulties, driven by a 60W/ch integrated
amplifier (Audiolab 8000A Mk II). I also listened to them at a
showroom driven by a 100W/ch power amp, and I heard a difference
in the region where the 1090is appear to have an emphasis:
midbass. On "True Lies", when the helicopters arrive at
and leave the island just before the nuclear bomb goes off (now
where would anyone get the idea we live in a violent world?), the
"WHUP! WHUP!" of the rotors was overly emphasized in my
listening room. When I heard the exact same scene at the dealer's
showroom, the emphasis was still there, but it was never
intrusive. So, again, placement of the bipolar speakers is
crucial.

I also tested the 1090is with a subwoofer
(the HSU HRSW12V with the standard 91Hz HP/LP). In this setup,
the 1090is were relieved of much of the 90Hz signal and below
(the HSU employing a 24db/Octave high pass) information. Much
better.

Conclusion

All in all, the Mirage 1090is are a very,
very good value for the money. From the bottom up, the sound
spectrum wasn't seamless, but there is an excellent bass
extension, an emphasized (not unpleasant, on certain recordings)
mid-bass, and nice, clean highs.